If they were registered they’d show up someplace. And if they’re registered someplace other than where they currently live the registration is void.
The article’s point still stands.
Get out there and get the RIGHT people registered.
My point is that most of the 47 million white voters who did not vote in 2012 are probably registered to vote. It is probably not a registration problem - it is the fact that they simply have not voted in many election cycles.